1. Field of the Invention
The present invention relates to a method and apparatus for controlling an event of a cable modem and reporting a status of the cable modem. More particularly, the present invention relates to a method and apparatus for controlling an event of a cable modem and reporting a status of the cable modem that may request a transmission bandwidth of a CM-STATUS message using a periodically allocated polling interval as well as a contention interval, when a mode allocated for the transmission bandwidth of the CM-STATUS message is determined as the polling mode.
2. Description of the Related Art
A cable modem termination system (CMTS) and a cable modem according to a Data Over Cable Service Interface Specification (DOCSIS) 3.0 standard adopt a channel combination scheme that may transmit data via a plurality of upstream channels and downstream channels.
The cable modem capable of simultaneously transmitting and receiving data via the plurality of upstream channels and downstream channels may periodically receive a MAC Domain Descriptor (MDD) message via all the downstream channels included in a Media Access Control (MAC) domain. Here, the MDD message transmitted via a primary channel may include a set of available upstream channels and downstream channels that the cable modem may use, and control and setting information associated with the MAC domain. For example, the MDD message may include parameters associated with a CM-STATUS message reporting mechanism that is used after registration of the cable modem. When an event occurs, the cable modem may transmit the CM-STATUS message to the CMTS to thereby inform the CMTS about the occurrence of the event. The MDD message periodically transmitted by the CMTS may include information regarding an event type code that may need to be reported using the CM-STATUS message, a holdoff timer indicating when to transmit the CM_STATUS message, a maximum number of transmittable reportings, and the like.
When an event control encoding associated with the CM-STATUS message is not included in the MDD message transmitted via the primary channel, the cable modem may not transmit the CM-STATUS message to the CMTS although the event occurs.
The CMTS may control reporting about the event of the cable modem, or may instruct the cable modem to take an appropriate action for the occurrence of the event, using a CM-CTRL message. For example, the CMTS may transmit enable bistmask information associated with each of events of CM-STATUS and thereby control whether to report a corresponding event.
FIG. 1 illustrates a format of a CM-STATUS message according to a conventional art.
Referring to FIG. 1, the CM-STATUS message may include a transaction identification (ID) 102 and an event type 103 indicating which event occurs, and type/length/value (TLV) encoded information associated with a corresponding event, behind a MAC management message header 101. FIG. 2 is a table illustrating types of events reported by a cable modem using the CM-STATUS message.
In the case of the events as shown in FIG. 2, when corresponding objects are enabled, the cable modem may report the occurrence of a corresponding event to a CMTS using the CM-STATUS message. Parameters associated with an event type may include a downstream channel identifier (ID), an upstream channel ID, a Downstream Service ID (DSID), and the like.
Since the cable modem remembers that each of the events is in an “on” status or an “off” status, the cable modem may report to the CMTS about a situation where a corresponding event triggers the “on” status, or resets to the “off” status. Reporting of the event status may use a maximum holdoff timer value and a maximum report count value that are obtained from an MDD message. Here, the maximum holdoff timer denotes a point in time for transmitting the CM-STATUS message, and the maximum report count denotes a parameter about a number of transmissions.
In a Hybrid Fiber Coax (HFC) network, in the case of an upstream transmission, a plurality of cable modems may access a single CMTS to share an upstream bandwidth. Therefore, the CMTS may designate a particular cable modem, among the plurality of cable modems, to perform an upstream transmission. Specifically, a cable modem may request the CMTS for a bandwidth allocation. When the cable modem is assigned with an opportunity for the upstream transmission, the cable modem may have an opportunity to transmit a message to the CMTS. When an event occurs whereby the cable modem desires to transmit the CM-STATUS message, the cable modem may need to request the CMTS for a bandwidth allocation in order to transmit the message.
FIG. 3 illustrates a mechanism for transmitting a bandwidth allocation request message of a cable modem in a contention-based transmission interval according to the conventional art.
Referring to FIG. 3, when an event occurs in an interval 303, the cable modem may verify a contention transmission interval using a received upstream bandwidth allocation map 301, calculate a transmission opportunity using a backoff window value, and wait for the transmission opportunity by the backoff window value, and then transmit a bandwidth allocation request message 305. When the cable modem recognizes a collision 307 after the request, the cable modem may retransmit another bandwidth allocation request message 309 according to a Truncated Binary Exponential Backoff (TBEB) policy.
Here, the contention based transmission interval is allocated for only a particular cable modem. Thus, when a plurality of cable modems simultaneously performs a transmission, a collision may occur. When the collision occurs, the plurality of cable modems may need to increase a contention backoff window value and then perform a retransmission according to the TBEB policy, which results in a delay 311.
When an event that needs to transmit a CM-STATUS message occurs, a cable modem may transmit the CMTS message according to a bandwidth request using a contention scheme or a piggyback scheme. The piggyback scheme denotes a scheme that may simultaneously transmit data and request a bandwidth required for a header. Therefore, while the data is not being transmitted, reporting may need to be performed through the bandwidth request using the contention scheme. In this instance, when many cable modems access a network, or when an inter-network event occurs in a plurality of cable modems, a collision may occur in making the bandwidth request. In this case, reporting to the CMTS about the event occurrence of the cable modem may be delayed.
Accordingly, there is a need for a method that enables a cable modem to quickly and effectively report to a CMTS about a status of an event occurring in the cable modem, and enables the CMTS to quickly recognize the event occurrence of the cable modem.